hi, i'm working with reactivision and i'm building a visual feedback of fiducials' positions and movement with GEM.

Since the coordinates given by reactivision range from 0 to 1for y axis and 0 to 1.33 for x axis (actually 0 to 1 as well, but i stretch it to get right values when calculating distances).

Opening gemwindow with the default viewpoint and a window dimension of 640x480, ranges are [-4;+4] for y axis and [-5.3;+5.3] for the x axis.

I will have to translate and strech the coordinates, but i know that i can change the view in the gem window, so i thought i could just find a view that shows me the [0;1.3]x[0;1] portion of the "gem space".

I know the gem space is 3D and to achieve what i need i should play with the z value in the view message, but i can't figure out how the view modification works. For example, which view corresponds to the default view obtained with no messages?

And, do you think this could be a good "trick", or is it better to just perform a coordinate translation?

thanks,
athos

Performing a coordinate translation seems the best solution to me.

For y axis: [gem Y coord] -> [+ 4] -> [/ 8], now the range is [0; 1]
For x axis: [gem X coord] -> [+ 5.3] -> [/ 10.6] ->

• now the range is [0; 1.3]

Am I missing something?

thanks guido, i will just go with the coordinate translation, but i need to translate tuio coordinates to gem coordinates, so i will basically need the inverse of your calculations:

tuio-y-coordinate * 8 - 4 = gem-y-coordinate
tuio-x-coordinate * 8 - 5.32 = gem-x-coordinate

the multiplication factor is the same for both axes, since i already strech the x axis as soon as i receive the tuio data (actually, due to the 4/3 aspect ratio, the stretching factor is 1.33... )

thanks a lot!
athos